Auchenorrhyncha were sampled from control, fertilizer-and sludge-treated plots within agricultural and fourth-year old-field communities. (2) Nutrient enrichment significantly increased net primary productivity in both plant communities. (3) Functional plant community properties (e.g. net primary production) were more robust indicators of nutrient enrichment than were structural properties (e.g. plant species diversity). (4) Nutrient-enriched plots generally exhibited higher Auchenorrhyncha population densities than control plots in both community types; differences were more frequent in the more mature old-field community. (5) There were significant differences in Auchenorrhyncha species richness only in the nutrient-enriched plots in the old-field community. (6) Changes in Auchenorrhyncha density and diversity were attributed to changes in plant composition, productivity and probably plant quality and vegetational architecture. (7) Auchenorrhyncha within the more mature old-field community exhibited a greater response to nutrient subsidy than within the agricultural community; these differences were attributed to plant-insect life-history characteristics.